Broadband mode division multiplexer using all-fiber mode selective couplers.

Area of Science:

• Optical Engineering
• Telecommunications
• Materials Science

Background:

• Mode division multiplexing (MDM) is crucial for increasing optical fiber communication capacity.
• Existing MDM devices often suffer from narrow bandwidth and complex fabrication.
• All-fiber devices offer advantages in mechanical stability and integration.

Purpose of the Study:

• To develop a broadband all-fiber mode division multiplexer (MDM).
• To achieve efficient multiplexing of multiple spatial modes over a wide wavelength range.
• To demonstrate the feasibility of cascaded mode selective couplers for MDM.

Main Methods:

• Fabrication of mode selective couplers by precisely matching effective refractive indices between few-mode fiber and single-mode fiber.
• Cascading these couplers to create the MDM device.
• Characterization of coupling efficiency, mode extinction ratio, and far-field patterns across the S, C, and L bands.

Main Results:

• Achieved a significantly broadened bandwidth potentially spanning S, C, and L bands.
• Demonstrated high coupling efficiency (>55% worst-case) for 4 spatial modes from 1515-1590 nm.
• The all-fiber construction ensures excellent mechanical stability.

Conclusions:

• The developed all-fiber MDM based on cascaded mode selective couplers offers broadband operation.
• This technology provides a stable and efficient solution for increasing optical communication capacity.
• The device performance validates the design approach for future integrated photonic systems.